It is worth pointing out that the mishearing or misunderstanding of instructions in English, and the use of another language, in an international conversation, ______ two recent aircraft accidents.

A．leading to

B．to lead to

C．led to

D．have led to

工业水系统应在（）投入运行。

A.锅炉点火前

B.锅炉点火后

C.机组冲转前

D.机组并列后